Trans fats keep food fresh longer while they're on grocery store shelves. However, the partially-hydrogenated oils can also lead to heart disease because of the increase in low-density lipoprotein LDL-cholesterol and decrease in high-density lipoprotein (HDL) cholesterol. Here are tips to control trans fat intake. (Source: CDC) (Chicago Tribune)

Girl Scout Cookies, whose ordering season finished last week in the Chicago area, came with an extra pledge this year.

For the first time ever, the scouts could promise that the majority of the cookies on the order form — five of eight varieties — contained no hydrogenated oils. In other words: No artery-clogging trans fats.

That was great news for health-conscious cookie lovers who didn't order Samoas, Tagalongs or Thin Mints. Despite carrying a "0 grams trans fat" badge since 2007, these three — most popular cookies on the roster — still feature partially hydrogenated oils as their second and third ingredients.

This inconsistency is allowed under rules from the Food and Drug Administration, which mandated labeling on artificial trans fats starting in 2006 but allows products to be marked "0 grams trans fat" as long as the amount falls below 0.5 grams per serving.

In this case of Samoas, that's two cookies. So a person who eats eight of them could be taking in nearly 2 grams of trans fats — a substance the National Academy of Science says cannot be safely consumed in any amount.

Health advocates are agitating for change in the FDA's rules, saying this loophole in labeling gives consumers no way to accurately assess how much trans fat they may be consuming.

In an article published this month in the American Journal of Health Promotion, Eric Brandt, of Case Western Reserve University Medical School, urged the FDA to require manufacturers to disclose trans fat levels in 0.1-gram increments.

The medical student used examples from average American diets to show how consumers could easily eat high levels of the fat without realizing it.

"The overall goal of the (move) is to provide another tool for consumers to control their own health and well-being," Brandt said.

The FDA said in a statement that it agrees "trans fat intake should be limited as much as possible."

"FDA is currently assessing strategies to further limit the use of artificial trans fat in the food supply now that we have more sensitive methods for detecting trans fats in foods at concentrations lower than 0.5 grams," the statement said.

The department did not provide specifics on the reassessment or say when it might be complete.

While the FDA does not yet require labels to disclose trans fat amounts below 0.5 grams, a study by the Center for Science in the Public Interest found that most foods labeled "0 grams trans fat" that list partially hydrogenated oils in the ingredients usually deliver about 0.3 grams per serving.

Neither the Girl Scouts of the United States of America nor its two bakers, which includes the Kellogg-owned Little Brownie Bakers, would reveal how much trans fat is in its three most popular cookies, saying only that they meet FDA standards for "0 grams trans fat" labeling.

"We are always looking for ways to make healthier cookies that still appeal to our audience," said Girl Scouts spokeswoman Michelle Tompkins. "Our bakers are constantly tweaking the recipes, but we do know that our girls are selling a beloved American treat that is to be enjoyed in moderation."

Girl Scout Cookies are by no means alone in the trans fat troop. While Oreos phased out trans fats in 2006, Chips Ahoy, Nilla Wafers and Nutter Butters, among others, can claim to contain zero grams of trans fat while including partially hydrogenated oils among their ingredients.

Artificial trans fats (also known as trans fatty acids or partially hydrogenated vegetable oils) are created by pumping hydrogen into vegetable oil to make it solid. Small amounts also occur naturally in the meat and milk of ruminant animals, but it is unclear if they have the same health effects as artificial trans fats.

Partially hydrogenated oil came into wide use over the last century because of its ability to add cheap flavor, texture and shelf life to foods, especially baked goods. It has also been widely used in commercial frying because the same oil can be used several times.

In the early '90s, however, scientists started to find that trans fats caused elevated levels of bad cholesterol (LDL) and reduced levels of good cholesterol (HDL), while increasing the risk of heart disease and stroke. It has also been associated with higher levels of Type 2 diabetes.

Under pressure from consumers and health advocates, several food companies, including the two bakers for the Girl Scouts, have tried to remove or reduce trans fat in their products. Some have removed it altogether, while others have simply reduced it to levels that still allow the "0 grams trans fats" label.

While the American Heart Association advises limiting average trans fat consumption to no more than 2 grams a day, the Institute of Medicine advises completely avoiding manmade trans fats.

The Center for Science in the Public Interest has encouraged the FDA to enforce more specific labeling, modeled on Canada's limit of 0.2 grams per serving for a product claiming to be "trans fat free." But Michael Jacobson, executive director of the center, says an even better solution would be a national ban.

"The fact is that trans fat has no place in the food supply," he said. "The FDA could get rid of trans fats almost instantly by simply banning partially hydrogenated oil. … And I'm surprised that the Girl Scouts aren't being leaders in the area of trans fats."

While the FDA reassesses its strategies on limiting trans fats, industry forces may end up making a bigger impact. Last week Walmart, the world's largest retailer, announced it will stop selling products that contain any artificial trans fats in 2015.